Multi-phase Microfluidic Devices for Characterization of Circulating Tumor Cells in Breast Cancer Oncogenesis is a multi-step process leading to a variety of genetic changes with alterations in the transcriptome, and adaptive changes responding to treatments. Therefore, monitoring the dynamic alteration of cancer is critical for cancer treatment. We have integrated multiple microfluidic modules developed in our R21 into a Multi-Phase Single Cell Analyzer (MSCA) for circulating tumor cells (CTC) enumeration and single CTC characterization. Combining the robustness of microstructure, preciseness of optical manipulation and mobility of droplet, the integrated MSCA isolates and encapsulates individual CTC into droplets for nanoliter molecular analysis. With the ability to characterize CTC in routine blood draws, the integrated platform will transform the minimal invasive CTC assessment into a powerful tool for cancer treatment evaluation in hospitals and clinical laboratories, and realize personalized medicine for cancer treatment.